A Tuscan by birth, he originally served as an ambassador from Géza II of Hungary, but decided to remain in Sicily after a diplomatic mission.
He threw lavish banquets, which he used to begin a whispering campaign against Richard Palmer, Bishop of Syracuse, a rival candidate for the vacant archbishopric of Palermo (1166).
Likewise, he convinced the Grand Protonotary Matthew of Ajello that Palmer was planning to kill him and very nearly started a blood feud.
Nevertheless, Gentile swore an oath of fealty to Stephen just before the latter moved the court to Messina, where the conspiracy was uncovered and the "leader" of the group, Henry, Count of Montescaglioso, arrested and imprisoned.
Nonetheless, Gentile's penchant for conspiracy and sedition had apparently been satisfied and he took no part in any more such quarrels, dying early in 1171 and succeeded by Bartholomew.